Effect of Pulsed Electric Field on the Inactivation of Microorganisms in Grape Juices with and without Antimicrobials

The combination of different obstacles such as moderately high temperatures (<50 °C), antimicrobial compounds and pulsed electric field (PEF), to reduce naturally occurring microbes in red and white grape juices was explored. The microbial count decreased with the increase in electric field and temperature treatment when a constant number of pulses were applied. In red grape juice, up to 5·9 log reductions in counts were achieved by applying 20 pulses of 65 kV/cm (peak-to-peak) at 50 °C with 2 h incubation of the juice containing 1:3 lyso:chrisin (1:3 ratio of lysozyme and nisin; 0·4 g/100 ml). A log reduction in count of 6·2 was achieved at 51 °C when 20 pulses of 80 kV/cm (peak-to-peak) were applied with nisin addition (400 U/ml). A reduction in count of 4·4 log was achieved when 20 pulses of 65 kV/cm (peak-to-peak) were applied at 50 °C to white grape juice containing lyso:chrisin (0·4 g/1000 ml). There was no vitamin C reduction due to the treatment.